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/* Startup code compliant to the ELF Mips ABI.
Copyright (C) 1995 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA. */
/* This is the canonical entry point, usually the first thing in the text
segment. The SVR4/Mips ABI (pages 3-31, 3-32) says that when the entry
point runs, most registers' values are unspecified, except for:
v1 ($2) Contains a function pointer to be registered with `atexit'.
This is how the dynamic linker arranges to have DT_FINI
functions called for shared libraries that have been loaded
before this code runs.
sp ($29) The stack contains the arguments and environment:
0(%esp) argc
4(%esp) argv[0]
...
(4*argc)(%esp) NULL
(4*(argc+1))(%esp) envp[0]
...
NULL
ra ($31) The return address register is set to zero so that programs
that search backword through stack frames recognize the last
stack frame.
*/
#ifdef PIC
/* A macro to (re)initialize gp. We can get the run time address of 0f in
ra ($31) by blezal instruction. In this early phase, we can't save gp
in stack and .cprestore doesn't work properly. So we set gp by using
this macro. */
#define SET_GP \
.set noreorder; \
bltzal $0,0f; \
nop; \
0: .cpload $31; \
.set reorder;
#endif
.text
.globl _start
_start:
#ifdef PIC
SET_GP
#endif
move $31, $0
/* $2 contains the address of the shared library termination
function, which we will register with `atexit' to be called by
`exit'. I suspect that on some systems, and when statically
linked, this will not be set by anything to any function
pointer; hopefully it will be zero so we don't try to call
random pointers. */
beq $2, $0, nofini
move $4, $2
jal atexit
#ifdef PIC
SET_GP
#endif
nofini:
/* Do essential libc initialization. In statically linked
programs under the GNU Hurd, this is what sets up the
arguments on the stack for the code below. Since the argument
registers (a0 - a3) saved to the first 4 stack entries by
the prologue of __libc_init_first, we preload them to
prevent clobbering the stack tops. In Hurd case, stack pointer
($29) may be VM_MAX_ADDRESS here. If so, we must modify it. */
#if (__mips64)
dli $4, 0x10000000000
bne $29, $4, 1f
dsubu $29, 32
sd $0, 0($29)
sd $0, 8($29)
sd $0, 16($29)
sd $0, 24($29)
1:
ld $4, 0($29)
ld $5, 8($29)
ld $6, 16($29)
ld $7, 24($29)
#else /* __mips64 */
li $4, 0x80000000
bne $29, $4, 1f
subu $29, 16
sw $0, 0($29)
sw $0, 4($29)
sw $0, 8($29)
sw $0, 12($29)
1:
lw $4, 0($29)
lw $5, 4($29)
lw $6, 8($29)
lw $7, 12($29)
#endif /* __mips64 */
jal __libc_init_first
#ifdef PIC
SET_GP
#endif
#if (__mips64)
ld $4, 0($29)
ld $5, 8($29)
ld $6, 16($29)
ld $7, 24($29)
#else /* __mips64 */
lw $4, 0($29)
lw $5, 4($29)
lw $6, 8($29)
lw $7, 12($29)
#endif /* __mips64 */
/* Call `_init', which is the entry point to our own `.init'
section; and register with `atexit' to have `exit' call
`_fini', which is the entry point to our own `.fini' section. */
jal _init
#ifdef PIC
SET_GP
#endif
#if (__mips64)
dla $4, _fini
#else /* __mips64 */
la $4, _fini
#endif /* __mips64 */
jal atexit
#ifdef PIC
SET_GP
#endif
/* Extract the arguments and environment as encoded on the stack
and set up the arguments for `main': argc, argv, envp. */
#if (__mips64)
ld $4, 0($29) /* argc */
daddu $5, $29, 8 /* argv */
dsll $6, $4, 3
daddu $6, $6, 8
daddu $6, $5, $6 /* envp = &argv[argc + 1] */
#else /* __mips64 */
lw $4, 0($29) /* argc */
addu $5, $29, 4 /* argv */
sll $6, $4, 2
addu $6, $6, 4
addu $6, $5, $6 /* envp = &argv[argc + 1] */
#endif /* __mips64 */
/* Call the user's main function, and exit with its value. */
jal main
#ifdef PIC
SET_GP
#endif
move $4, $2
jal exit /* This should never return. */
hlt: b hlt /* Crash if somehow it does return. */
/* Define a symbol for the first piece of initialized data. */
.data
.globl __data_start
__data_start:
#if (__mips64)
.dword 0
#else /* __mips64 */
.word 0
#endif /* __mips64 */
.weak data_start
data_start = __data_start
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